Re: PDQ

On Wed, 22 Oct 2003 19:14:12 -0400, David E. Grove wrote: Yes! This is why my dostats utility explicitely sets PDQPRIORITY to zero (or a value specified with the -P option) for stored procedure updates regardless of the PDQPRIORITY value in the user's environment (or specified in the -Q option). Art S. Kagel >> makes a big difference to stuff like index creation and update stats. > > We learned to be careful with PDQ and UPDATE STATISTICS. > > In a past job, I had been working mainly with a data warehouse. In that > environment, I made constant and effective use of PDQ, and didn't think > anything of it. Very few users. Very few stored procedures. No problems. > Great performance. > > In present job, one day I cranked in a little PDQ to speed up UPDATE > STATISTICS (tables and procedures). About 15 minutes after UPDATE STATISTICS > routine finished, the system ground to a halt. Bottom line was that all the > stored procedures were prepared according to the environment that existed when > the preparation was done (PDQ cranked in, so multithreaded, etc.). Now the > current system is OLTP, not a warehouse. So, has a few hundred users and 1000 > SPs. As users started using the newly compiled SPs, they started sucking up > ever increasing resources. There was continual allocation of virtual memory > (several times a minute). Within 15 minutes, all memory was allocated, and > system was effectively dead. > > Solution was to rerun UPDATE STATISTICS with 0 PDQ, and everything went back > to normal. > > My lesson was learning not to be so "free and easy" with PDQ. Still a good > thing where appropriate, though. > > DG > > > "Obnoxio The Clown" <obnoxio@hotmail.com> wrote in message > news:bn42df$t1sn3$1@ID-64669.news.uni-berlin.de... >> Markus Bschorer wrote: >> >> > Hi guys, >> > >> > since the price-differences betwen IDS 9.4 and IDS 9.4 WE are not marginal, >> > I wondered, whether it's worth to buy a IDS 9.4 in order to be able to use >> > PDQ. May be it's better, to invest the difference-amount in better >> > hardware. >> > >> > Does anyone of you have expieriences in using PDQ and it's benefits >> > concerning Query-Performance? >> >> Only if you're doing big, heavy, table scanning queries, really. But it > also >> makes a big difference to stuff like index creation and update stats. >> >> -- >> Ciao, >> The Obnoxious One >> >> "Ogni uomo mi guarda come se fossi una testa di cazzo"